Unisolar PVL 68 questions

[Lafnbug]

Hello everyone. I am in my conceptual phase, but do have a Frankenlist of pieces I hope to fit together. My set-up will be the obligatory 'contractor' van, which I now own. It will be a 'live-in, work out of' project. I hope to be able to run a fridge, Fantastic fan, a few LED lights, and occasionally a few power tools (deWalt 18v, with a custom adapter to plug into a 12v socket). Will need to charge tool batteries, laptop, cell phone when necessary. I know I'm probably pushing the limits of my proposed system, but I am hoping that with judicious power usage, I can get by. Now, for a barrage of questions!

I have lucked into three of the UniSolar PVL 68's, with MC3 connectors. These should give me a peak of 204v in full sun (10a peak each, I think). First question is, how do I connect all 3 together? Is there a recommended 'bus bar' or other weather tight connector for this purpose?
Where is a good place on the van to bring the cables in? I will drill through the roof if necessary, but hoping not to.

What would be your recommendation for a MPPT controller? I don't want to skimp here; I want the best reliability/longevity first, most amount of user control second, adjustable 'float' if recommended, and a nice readout to monitor everything. Cost as necessary for above req's, but don't want to break the bank if possible.

For batteries, I am leaning towards four T105's. However, I am open to suggestions on this. I don't think my space will let me use more than 4 batteries, BUT I may try later to squeeze more in there if necessary. How many will I be able to charge in a day with 204v/30a?

I have a Chicago Electric 10K/5K continuous modified wave inverter. Not my first choice, but I plan to also have it connected to the vehicle for the times when I need major power. I will need a battery selector and separator I assume. I want to be able to charge my house batteries from the alternator when driving, and I also want to use the house batteries to start the van if necessary. Where can I find some info on this?

Okay, that's enough for now! Thanks in advance for the use of your neurons!

 

[akrvbob]

You will need two sets of these combine them all down to one:
http://www.amazon.com/HQRP-T-branch-Connector-Photovoltaic-Coaster/dp/B004N6V5LK/

I'm a big fan of Blue Sky controllers, but there are many good brands. I have the Blue Sky 2000E.

T105s are good batteries! Four may be a little too much, but no harm in having extras. Most people just use 2 but then they find themselves floating early in the day and wasting all that solar power.

No problem charging from the alternator at the same time. Just use a continuous duty solenoid to protect the starting battery from accidental discharge.

For jumping the starting battery, I would go low-tech--jumper cables! Then you can jump someone else if they need it.
Bob

 

[SternWake]

You will have approximately 200 watts of solar with three pvl-68. You will get about 12 to 13 amps in full summer high noon sun, depending on latitude and temperature and wiring.

These panels do pretty good in lower light or cloudy conditions, better than framed panels, but they take up a lot more room to make the same wattage in direct sun.

4 t 105's is a lot of capacity for that relatively little amount of solar. If you were to use 50% of that capacity, it would take more than 3 days in good sun, without any more loads placed on those batteries during those 3 days, for them to near 100% via solar alone.

Now any solar is better than no solar, but it is better( for battery longevity and performance) to have enough solar to meet a MINIMUM 5% of overall battery capacity. 5-13% is a figure someone else figured out a while back.

5% of 464 amp hours( 4 t105's) is 23.2 amps. Or somewhere between 300 and 350 watts of solar. Another good general rule which will see you through the cloudy days better is 100 watts per 100 Amp hours of storage capacity, so 200 watts for 464 amp hours of battery, is not doing those batteries any favors.

I deliberately lowered my overall capacity by 100 A/h as I wanted to come closer to the battery manufacturer recommended minimum charge rate. Also I never really needed all the capacity I was carrying. In fact it was extremely rare for me to go below 65%, and that took a few days of being electrically greedy and lots of bad weather.

I am cycling a single group 31 battery rated at 130 Amp hours with 198 watts of solar @32N.
I've been using a Bluesky2512i charge controller since 2007. I also have the IPN pro remote battery monitor so I can see what is coming from and going back into the batteries via several different charging sources.The IPN pro remote also allows one to change voltage setpoints, which can be vital for T 105's and they require 14.8 volt acceptance/absorption voltages to fully charge. I change my setpoints every 10 to 14 days to go upto near 16 volts on my group 31 battery, to get the specific gravity back up in the green(1.280). If I do not do this, after 3 weeks the voltage really falls fast under discharge, even after a blinking green light from the solar controller every day for several hours, and the Specific Gravity, despite the green blinking light, is down in the red at 1.225


Do not trust that a blinking green light means the batteries are really topped off. Only a Hydrometer can tell you that.

It is important to be able to bring the batteries back upto 100% regularly. If you just cycle them in the 50 to 80% range or less for weeks on end, they will sulfate badly and lose capacity quickly, and at that point, even doing an equalization( intentional overcharge) will likely return only a small portion of that lost capacity.

So if solar is to be your primary charging source, you need more solar or less battery, and you can't fit more than 3 pvl 68's on a Van roof, another option would splitting the 4 t015's into two banks and recharging one at a time.



If you really require 4 t-105's you will also need other charging sources. The alternator is a great bulk (back upto 80% state of charge) charger, if wired properly and driven long enough, but very poor at taking it them 100%.

Getting that last 20% into batteries takes hours and hours no matter what charging source is used. Do not believe any claims about fully recharging battery or battery bank, in less than 6 hours.

Solar is great for that last 20% but it needs to be enough solar that it can hold 14.8 volts for a few to several hours daily, and the more battery capacity, the more wattage required to hold them up in that range. One is basically shooting to have the batteries up above 80% by 11 am so there is enough sun and light left that the solar can hold 14.8 for the manufacturer recommended, or Hydrometer dictated time required to return Specific gravity to the maximum baseline.

Also if one is loading the batteries during recharge, then even less solar amps are making it to the batteries.

A plug in charger will be needed too for whenever you have access to 120Vac. Iota DLS 55 would be a good mate for 4 t 105's. It will do 14.8v which is important for t 105's.

I like my Blue Sky, but I hear good things about morningstar, and Rogue controllers too.

If I had to do it again, today I'd probably go with a single ~240+ watt framed panel, and a MPPT charge controller ( Rogue)which can handle 24v+ nominal panels. My controller is for 12v nominal panels only. I currently have a 130 watt framed Kyocera and a pvl 68 in parallel.

I wish I had bought the BS 2512i(x) model instead, which has a battery temperature sensor on it, which can be important if charging during temperature extremes.

Keeping the wires short as possible pretty much dictates drilling a hole in the roof. Google "cord grips". Dont stress the leak part if you do it right with the right product. Also keeps those wires from flapping around in the slipstream. Keep the charge controller close to the batteries over short fat cabling, but not in the same compartment.

Depending on the charge controller you get, you can run those 3 pvl 68 in series for higher voltages. Higher voltages translate into lower voltage drop across the wiring to charge controller, and thinner wiring can be used. There are higher penalties if a single panel is partially shaded though.

I am not aware of any solar specific combiner/junction boxes for RV's. I think some just use outdoor household boxes with watertight cordgrips for inlet and outlets.

Your MPPT charge controller's ability will kind of dictate whether you go with the panels in series or parallel, and this will directly relate to how or if a junction box on the roof is needed, and how clean of an install you can manage, and by clean I mean a short as possible circuit path through minimal connections over quality cabling/wiring for minimal voltage drop and best recharge performance.

4 t-105's will need to be vented. They will offgas a lot in the higher states of charging. You don't want to breathe/smell those fumes undiluted( closed van), nor do you want those fumes to accumulate somewhere where a spark can ignite them. Also the fumes are corrosive so no delicate electronics in the immediate area of the batteries either.

AGM batteries ($$$) are safer, if the battery bank is to be in the living quarters, and proper venting seems to be too much of an issue. The Iota's 14.8v might be a bit too high for AGM batteries.

Also one should not get 4 batteries and then add another 2 later on. Much better if all batteries in parallel, or series parallel are same size make and age.

Also can't stress enough the importance of proper wire/ cable terminations. Either crimping or soldering properly requires the right tools and the skills to use them properly. At best a bad connections will just heat up and waste power, at worst your van goes all Fukushima on you.

For inter battery connects and for cabling between alternator and batteries, I recommend having custom cables made up for those without the tools and skills.

Here is one place to have them made:
http://www.genuinedealz.com/custom-cables

So you can see it is not just a matter of getting batteries and adding a charging source, or 3. Batteries are not cheap so It is in one's best interest to recharge as close as possible to the manufacturer recommended rates, and really try to get them to a true 100% Monthly, if not weekly.

And never believe the blinking green light, until you verify it with a Hydrometer.

 

[Optimistic Paranoid]

If you really require 4 t-105's you will also need other charging sources. The alternator is a great bulk (back upto 80% state of charge) charger, if wired properly and driven long enough, but very poor at taking it them 100%.

Speaking of charging with your alternator, I ran across this recently.

Http://sterling-power-usa.com/alternatortobatterycharger.aspx

Looks interesting.

Regards
John

 

[Optimistic Paranoid]

Btw, as far as drilling through your van roof for wires and keeping things dry inside, the boating world solved this problem a long time ago. They call them cableclams. You can find them at Amazon if you search on that term.

Regards
John

 

[cyndi]

Be aware that your Unisolar panels may be high voltage and need a controller that can handle the load. I have more than one friend whose controllers or inverters (can't remember which of if it was both) were ruined because they weren't aware. Fortunately for me, a friend figured that out before I hooked the panel up. I had to upgrade my controller to the tune of $500.00.

 

[Lafnbug]

Thanks for the comprehensive responses! Looks like it's back to the proverbial drawing board. Being that I will not be able to expand on the amount of solar panels due to lack of space, I will take SternWake's advice and let my panels dictate the rest of the system. I'm more interested in a properly matched and designed system, then learning it's capacities, my needs, and working within it's constraints. This is difficult for me as I have no reference; this is my first solar project!

FWIW, I will be building a 'master panel' of light switches to enable me to turn off every electrical outlet or device individually. This is an effort to maintain total control over phantom loads, and just use what I need if I start to draw the batteries down too much.

I am not dead-set on the T105's; it just seems that many others have gone this route , and seem to like them very much. Are the AGM's a true deep cycle battery? Is there any weight difference in the AGM's? From what I've read, they seem to work fairly well but are sensitive to overcharging. This is the reason for my wanting the best charge controller possible ($), and building a 'matched' system. Believe me, I will completely overkill on cable oversizing, and short runs! I am very detail oriented, so I don't anticipate any problems.

As far as batteries, what other choices would you all recommend? I have no problem building a properly vented box if necessary. Put it this way; I want to build a quality system so my batteries LAST. To me, this may be more important than overall capacity. I can only afford to build this once. Is it realistic to get 8-10 years from your batteries?

As well, there is a dizzying array of refrigerators out there. Will my system be able to support any of them? I'll take what I can get on this one, anything is better than nothing...

FWIW, I try to live by this: "buy the best, and cry ONCE"!

Thanks again, everyone, for the comments, links, ideas, and time!

 

[Lucky mike]

if you get 8-10 yrs out of a battery bank you will be in the record books....if properly charged and looked after 5yrs is a good number

 

[Optimistic Paranoid]

AGM is a type of battery construction. Using AGM construction, a battery manufacturer can design it as a starting battery, a "marine" battery, or a true deep cycle battery.

Optima makes all three, and differentiates them by the color of the top. They make Red tops, Blue tops, and Yellow tops. (Btw, I don't recomend Optima brand, they are widely reported to have quality control problems and a poor customer service attitude.)

Lifeline makes high quality true deep cycle AGM batteries.

Can they last 10 years?

I recommend that you download the Lifeline battery technical manual from their website. It's a fascinating and enlightening read.

Towards the back they have several graphs, including one on expected life cycles.

Lifeline claims that if you pull 90% of the amp-hours out of their batteries, they will only survive 500 recharge cycles. (Btw, if you did that to a starting battery, you'd be lucky to get 50 cycles out of them.)

Lifeline says that if you pull 50% of the amp-hours, you'll get 1000 cycles.

If you only pull 10% of the amp-hours, you can expect 5000 recharge cycles.

So, yes, it's possible. The question is, does it make ECONOMIC sense to have a battery bank that big and heavy, or does it make more sense to have half as many batteries and replace them twice as often?

Regards
John

 

[accrete]

AGMs...

I have a Parkliner Travel Trailer that has two Optima AGM batteries located under the street side sofa. From the factory it came with a PD 4045 (Progressive Dynamics) converter/charger as the go between 120v hookup and the two 12 volt AGM batteries.

After much research, and discussion with both Optima & PD tech support, i came to the conclusion that the batteries were not going to be happy without a better charging solution. What i ended up doing is installing Optima's Digital charger...i can say that the batteries are now quite happy.

All that said to say that AGMs are particular in what they want. I can understand that this was the best solution for the interior install. Though i did feel the need to go one step further and install venting for the battery box to the outside and separate the batteries from the charging electronics. It was a fun project but worth the peace of mind to know it is safe.

Here are a couple pix of how things are set up in our little fiberglass trailer:

Best wishes on the build.
Thom

 

[Lafnbug]

Thanks for all the info everyone; I'm going to take some time and keep reading before I make any other purchases. I vastly underestimated the complexities and choices available for these systems. That's OK; I like to learn. I will start another thread once I get up to speed, so to speak, so I can ask better questions next time! Again, thank you everyone for your replies and help!

 

[Lafnbug]

Well, I just discovered HandyBob's Solar Blog. All I can say is WOW =:^)

I guess I'll start there....

 

[highdesertranger]

lafnbug just to let you know dewalt makes a 18v tool battery charger that runs off 12v. no need for anything custom. also better than running a regular one though an invertor. highdesertranger

 

[akrvbob]

This has become way too overcomplicated. Buy the combiner I recommended and a Blue Sky 2000E controller, and a pair of batteries. Buy an MC3 extension cable from Amazon long enough to go from the panel to the controller. Remember, you are going to cut it in half so it needs to be twice as long as you need. Plug the one end into the MC3 combiner and strip the other end to go to the controller. 10 gauge wire will be fine for the few feet you are going from the controller to the batteries. You'll want an inline fuse holder on the wire going from the positive of the solar controller to the into the positive post of the battery. And that's it, your done.

Personally, I'd buy a pair of T105s but if you are cautious and don't want unsealed batteries, buy a pair of AGM Sears Marine batteries on sale. If you have a battery place near you you can get better deep cycles like Lifeline AGMs or some other brand. I'm not a fan of Optima. I think you pay too much for what you get. But that may just be a prejudice.

The panels you have are 12 volt, so no need for a high voltage controller.

I've installed several of those Unisolar panels, and it really is very simple! Here are two posts I did on the install:

http://www.cheaprvliving.com/installing-flexible-solar-panels/
http://www.cheaprvliving.com/blog/installing-flexible-solar-panels-on-a-fiberglass-roof/

 

[SternWake]

AGM batteries are commonly lumped together as to their charging requirements, but in actuality, they can vary widely as to what the manufacturers recommend, and exceeding the recommendations can damage the batteries and fairly quickly too.

Flooded batteries are more tolerant of wider recharging regimens in this regard, and 6v golf cart batteries are generally just the best bang for the buck, and are true deep cycle batteries, where as Most, not all, 12v batteries which say "Deep Cycle" as well as marine and RV and trolling on the label, are just dual purpose batteries.

T 105s have a great reputation but the golf cart batteries sold at Costco and Sams club will yield better service than any dual purpose 12v battery, and likely any true 12v Deep cycle battery as well. GC-2 are a few inches taller than most batteries.

Many AGM's have much less internal resistance, so they naturally have high Cold cranking amps figures. Some other AGM's are not so impressive, spec wise, as to internal resistance, self discharge and fast recharge ability, and generally the lower the cost the AGM, the less impressive the specs, So be suspicious of AGM's that are not at least 2x the price of FLA's (Flooded lead Acid).

Note that AGM are still lead acid batteries. Do not confuse Gel batteries for AGM. They are different and more finicky as to recharge regimen and really not a good match for Vehicular use.

Not all sealed "maintenance free" batteries are AGM or GEL either.

the whole purpose of a regular engine starting battery commonly called SLI for Starting lighting ignition, is to provide short lived high bursts of power. To do this flooded batteries need many thin plates for maximum surface area.

Flooded deep cycle batteries have less numerous, but thicker more durable plates designed to give less power , but over longer periods and recover better from deep discharges.

Marine batteries are a dual purpose compromise between those 2 leaning more toward the starting battery than the deep cycle battery.

AGM batteries built as deep cycle batteries, will equal or perhaps still exceed the CCA ratings of the same size flooded battery.

There are some AGM manufacturers who will promote theirs as deep cycle, or High CCA ratings, and some that will promote both, but basically AGMs are true dual purpose batteries without being compromised like a flooded dual purpose marine battery is.

Some AGM batteries that say "marine" on them are identical tio the Automotive batteries , except for the addition of threaded posts in addition to the automotive posts.

Some AGMs like Lifeline or Odyssey say you can blast their batteries when depleted, with HUGE currents, like hundreds of amps initially, as long as the voltage is kept below a certain figure. I think Lifeline says 14.4v max. I know Odyssey( who makes sears die hard platinum) insist on 14.7v.

Other AGM batteries like the Asian AGM "universal battery" will say to limit recharge current to no more than 30% of the Amp hour rate measured at the 20 hour rate. So a 100 amp hour Asian AGM battery cannot be fed more than 30 amps. Where as a 100 amp hour Odyssey battery wants a minimum of 40 amps, when deeply cycled, and as such does not make a good contender for a primarily solar recharged battery.

I too am no fan of Optima. Their six pack design reduces overall battery capacity.
A group 31 Optima contains 75 amp hours and has 900 CCA
A group 31 Odyssey contains 100 amp hours and has 1150 CCA
They cost about the same. take up the same space, one just has 25% less capacity, but excellent marketing!

The Six pack design of Optima excels in high vibration, high physical stress on the battery case environments. Not exactly what one needs in an RV battery, not even close.


So you are wise to aim for a well balanced system. Many people decide on a battery capacity then allow it a certain amount of solar, and the solar really is just too underpowered for the capacity chosen. Too little solar can offset electricity used and lessen the amount that the battery is depleted, but cannot properly and fully recharge a depleted battery or battery bank.

So any solar is better than no solar, just as any and all charging sources are better than just letting a battery sit depleted, but if one hopes to get a 5 year lifespan from batteries cycled daily, they better be able to make the batteries happy by prompt full and regular recharges that come as close as possible to what the battery manufacturer recommends.

Now if this regimen is labor intensive or costly( running a genset for hours and hours), one must figure in the cost of just replacing the batteries sooner than expending huge efforts into getting the maximum service possible from them.

Everything is a compromise. The goal is to make that compromise beforehand, not find out afterward, and stress out looking for the fault, which might only be in the original planning stages

So a controller with adjustable voltage setpoints is wise so one can fine tune voltages for different batteries, as they are replaced.

It is difficult to have too much solar, but if you are limited to 3, 68 watt panels, then I would not exceed 232 amp hours that the common set of golf cart batteries contains, capacity wise. I would aim to take no more than 70 amp hours from those batteries nightly in summer on average and 55 amp hours in winter, and that is in a sunny environment. 116 amp hours removed would be the 50% mark.

Some say to have enough solar that it can replenish on a good sunny day, from the 50% mark, keeping in mind batteries require anywhere from 105% to 150% the energy taken from them to fully recharge them.

YOu can have more battery capacity, but you will need other charging sources besides solar and be able to employ them after days without reaching a full recharge, or falling below 50% regularly.

And as always, it is easier to use less electricity, than it is to create or store lots of it. Cook with propane, Use LED lights, DC to DC car adapters for laptops. USB charged devices should be charged by a 12v ciggy plug adapter, not an inverter powering the 120Vac transformer provided with the device. All those stick and brick amenities like electric coffee makers and toaster ovens and microwaves should not be transferred to battery power unless the ability to recharge the large battery bank is just as impressive as the large battery bank required to power such devices for any period of time

If a fridge is installed, A 12vDC compressor fridge consumes half of what a 120Vac dorm fridge powered by an inverter would consume. Keep the Interior from turning into an oven with good ventilation and sun shades and a light body color and good insulation, and that fridge will run 1/3 less and consume 1/3 less battery power.

If you are aiming at a cooler and block ice, well Block ice every 5 days for a year costs more than a 12v compressor fridge, not counting the cost of gas to go get the ice or the inconvenience of going to get it, or water and food filled zip lock baggies which can compromise your health.

With my 1.8 cubic foot compressor fridge and 198 watts of solar. I have no concerns about refilling propane, running out of battery, or food spoiling. It rocks.

Basically the inverter is the most wasteful device that everybody thinks is a solution to all ones power needs. A necessary evil perhaps, but it is better to not have to use one, rather than just view one as the cure all to electrical needs.

Do look more into the Rogue MPPT controller. I think it is one of the better and more adjustable MPPT controllers available, and should handle those 3 pvl 68's in series so have the option of using thinner wiring from junction box or MC3 combiner, to the controller.

Also MC3 cable is getting harder to find as MC4 has taken over. I bought some 10 awg mc3 cable and it has 7 thick strands in it. Not very flexible at all, and made routing the connecting the wires into my controller a serious PITA curse fest. I used 8 awg from the 130 framed panel to CC. 3 times as flexible and a joy to work with in comparison.

 

[flying kurbmaster]

thanks Sternwake for sharing your knowledge with us, very appreciated

 

[Lafnbug]

Thanks all, for the comments, links, suggestions, and photo's!

One of the reasons I decided to go with the PVL68's is their better shaded/low light conditions performance (MD has bizarre, rapidly changing weather); another is that they may be mounted permanently to a (slightly) curved van roof, with no provision for tilting. I assume that this mounting method is not optimum, as the panels are 'splayed' outwards from each other, meaning that at no time can all three be getting 100% direct sunlight. HOWEVER, I have a safari rack for this van, and am now considering mounting them FLAT on top of the rack on plywood/sheetmetal/other.

Benefits:
1. If the panels are mounted to boards or sheetmetal, I can move the array to another vehicle later, if necessary.
2. This will create a nice heat barrier above the van roof.
3. A tilting mechanism could be fairly easily fabricated for this set-up, although it would kill the desired 'stealth' qualities that I desire. It would be better for my times in the boonies, tho!
4. This puts the panels even higher, and slightly more hidden from street view.

Detriments:
1. The safari rack adds weight and wind resistance.
2. The rack design will also partially shade the PV's at low sun angles.

With all of this in mind, will wiring the panels in series be a better option? It is frequently overcast here; will I get better overall performance running them parallel?

My understanding is that PVL68's put out 68w, 16.5v, 4.13amps. So am I correct that with 3 in parallel I would get:
204w, 16.5v, and 12.39amps

Then in series I would get:
204w, 49.5v, and 4.13amps?

I understand that from and electrical efficiency standpoint, series allows the use of smaller gage wiring, and maybe less power loss getting to the charge controller? As well, would parallel be more efficient from an overcast sky condition?

SternWake, I read some of your previous posts about your Vitrifrigo C51i; I assume this is the unit you were referring to. Would my PV's, Rogue MPPT, and (2)T105's have a chance at operating this thing? It seems to me that summertime usage may be possible, which would be all I need; I don't need a refer in the winter! 70a/h at 3w gives me ~24hrs run time. Would this work? I'm not sure this would leave me much other energy to work with, other than perhaps some LED's...

---

3amp, not 3w....

 

[akrvbob]

lafnbug, there are advantages to series but the really big disadvantage is that few controllers are designed to handle that high voltage so you are going to have to spend a LOT more money for a controller. The cheapest High Voltage controller I know of is $200 (without a digital readout, the readout is another $90) and made by Blue Sky. My 240 watt panel is high voltage so it is what I have for it.

No, you have the math wrong. You do divide the watts by the voltage to get amps so if you are using a PWM controller you would divide the 204 by the voltage of the panel which is 16.5. But if you are using a MPPT contoller you divide 204 by 12. The MPPT steps down the voltage and increases the amps which a PWM can't do. With a PWM controller, everything between 12 volt and 16.9 is simply lost, thrown away. That's why you are better off spending the extra money and buying a MPPT controller, you'll get 35-40% more amps into your batteries.

A PWM will work only on low voltage panels so if you do them in series you MUST have a high voltage MPPT controller.

I have 190 watts on my trailer and have no problem running my 12 volt compressor fridge off it year around.
Bob

 

[SternWake]

Regular Metal van roofs have corrugations in them, so the unisolars would be bridging the peaks and trap water and leaves and other detritus below them, so the idea of mounting them to a flat surface to a rack is not a bad one. Also the sticky side under the bridges would trap that detritus, and lead to rust.

But as far as tilting the whole rack, well it will only really be effective morning and evening. The surface of the unisolars is Stippled to grab light from lower angles, so tilting them will not yield the same improvements that tilting a framed panel would.

I can tilt my framed panel. I almost never do. I do not need to.

My front loading fridge is residing in a cabinet with about 1.5 extra inches of insulation all around it, and the whole cooling unit is bathed in ambient air temps with zero chance to recycle any preheated air, so it is significantly more efficient than it would be if I just slid it into a cabinet without thought toward airflow, and turned it on.

Last week, when we had daytime highs in the 3 digit range and lows in the high 60's, It was still not using more than 24 amp hours in 24 hours.

Basically , with 198 watts of solar, I never worry about my fridge, it is always sub 35f inside, and I have plenty of battery power for other things too. I bet I could run two of these fridges in summertime no problem. I shudder to think about those years when I was driving to the store every 5 days for ice, or throwing out food on the 6th. Or dipping my hand into icewater for a beer, or fishing out a water filled ziplock baggie with contaminated food within.

I've been doing this since 2001, the compressor fridge and solar have been installed since '07, and is the best thing I have done to better this lifestyle.

With 2 t 105's you will have ~100 more amp hours of capacity than I do(*). So 6 more watts, 100 more amp hours capacity, even if you did not add extra insulation or fine tuned airflow across cooling unit, you will have no issues running the fridge, but do make attempts to keep the van interior cool, as if it bakes in the sun and goes upto 120f, well that will use a Lot more Juice. Do build the cabinet compensating for extra insulation, and to promote airflow through condenser and across compressor and controller.

My van is white and I have enough ventilation, and reflectix window shades that it is rare for my van to exceed ambient air temps, so this really lessens the load on the fridge too. Offsetting the electrical consumption of the 120mm, 92, 80 and 40mm computer muffin fans I am always running a few of, 24/7.

Since the PVL 68s harvest more in low light than my framed panel does, you will likely harvest more in the same location as I would, disregarding the 6 watts difference.

When i added the Unisolar 68 to my 130 watt framed panel, my solar charging amps doubled from first light to about 10:30 where it tapered to 50% more. Same again in the evening.

Ths Unisolars when new, for about 2 months or so, will make about 15% more than what they will after that 2 months have passed.

3 unisolars in series might be a bit much voltage for most any MPPT controller. 2 in series fine for many. On another forum, somebody experimented with framed panels in series vs panels in parallel and found the advantages of series were not as great as expected, and partial shading of a single panel in series really killed output.

But different panels respond differently to shading of one panel or partial shading of more than one so each case and setup is different and I would just be guessing how 3 pvls will respond one way vs the other, with little confidence in my guess..

You said you'll be using thick wire regardless, so probably just aim for parallel and a less expensive MPPT controller.

(*) I only cycle one of 2 of my batteries, either or, but not together. Really I have 220 amp hours total. I have no issues letting one battery feed the other if it came to it, temporarily, but I will not intentionally leave them in parallel when discharging. I did this because I was tired of carrying around a starting battery that was never used for anything but starting. I did not need a 230 amp hour house bank and another 115 amp hour starting battery. So I dropped one house battery and carry around 62 less Lbs. I use 3 Blue seas manual switches to switch my ignition, my loads and my solar to either battery. But I would not trust anybody else to fiddle with my switches, especially not with the engine running.

 

[Lafnbug]

Thank you Bob and SternWake. A much clearer picture is starting to emerge. I will keep you posted on my progress, although it will be a while before any happens. Currently downsizing to fund The Dream Machine =:^)

As of right now, I have a pile of parts, some drawings, and too many ideas! I really wanted to wrap my mind around this, as I have to gut my van, frame my layout, run my wiring, insulate, then execute a proper build-out - in whatever sequence it dictates.

I have a tendency to overcomplicate things!